1. Field of the Invention
The subject of the present invention is a safety device for vehicle electric window lifters of the type having a cable for driving the window using a motor, the cable passing around a return pulley.
2. Description of the Related Art
It is known that there currently exist three types of window lifter on motor vehicles: cable back window lifters, twisted cable (Bowden cable) window lifters, and arm and toothed sector window lifters. The invention relates to the first two types of window lifter.
When an obstacle is located in the path for closing the window, the system must recognise the presence of an abnormal phenomenon and, if the force on the window exceeds a limiting value, the window must not continue its journey, but stop and at least release the force. This release of the force may be obtained either by releasing the window which descends under a small force or under the effect of its own weight if the friction of the lateral seal allows it, or by reversing the movement of the window which is then forced to descend.
In order to solve this problem various electrical and electromechanical safety devices have already been proposed which exhibit, amongst other drawbacks, the drawback of being relatively costly due to their complexity. This high manufacturing cost is obviously an obstacle to their widespread distribution.